The present invention relates to a surface finishing apparatus and a related method and, more particularly, to a surface finishing apparatus and a related method for surface finishing a workpiece in a desired geometrical profile contoured along an axial direction of the workpiece.
In the past, various attempts have been undertaken to lap a target shaped periphery, such as a journal portion or a pin portion, of a crankshaft of an automotive engine and subsequently to roller burnish the resulting surface in a desired surface roughness.
The preceding lapping operation in such surface finishing is achieved by permitting the target shaped periphery of the workpiece to be covered with a lapping film and placing a plurality of shoes on a rear side of the lapping film whereupon, under a condition where the lapping film is held in pressured contact with the workpiece, the workpiece is rotated to allow an abrasive surface of the lapping film to lap the target shaped periphery of the workpiece. To this end, a lapping apparatus includes an urging mechanism that urges shoes against the workpiece through the lapping film, a drive unit to drivingly rotate the workpiecce, and an oscillating mechanism arranged to apply an oscillating force to at least one of the workpiece and the lapping film along an axial direction of the workpiece, as disclosed in Japanese Patent Application Laid-Open Publication No. H07-237116, with reference to FIGS. 1 and 2, and their corresponding descriptions.
However, since such mere lapping operation results in an outer circumferential periphery with an insufficient profile or in an undesired surface roughness, an attempt has been made to allow a burnishing roller to be brought into pressured contact with the outer circumferential periphery of the workpiece to collapse uneven surface portions of the outer circumferential periphery of the workpiece to provide an improved surface nature in the workpiece while permitting the outer circumferential periphery of the workpiece to be formed in a mid-concave profile for use as an oil sump to enable lubricating oil to be suitably supplied as disclosed in Japanese Patent Application Laid-Open Publication No. H06-190718, with reference to FIG. 11 and its corresponding description.
In the meantime, there is a probability where one type of workpiece needs to be surface finished in a highly accurate straightness, and the other type of workpiece is intended to have a geometric geometrical profile, positively formed in mid-convex or mid-concave shapes.
Also, depending on circumstances, for the purpose of improving a surface quality of the workpiece, a probability exists where the workpiece resulting from grinding operation is directly roller burnished without lapping the workpiece